public class Test {
    public static void main(String args[]) throws Exception{
        String html = "<tr><td>aa</td></tr><tr><td>bb</td></tr><tr><td>cc</td></tr>";
        Matcher m = Pattern.compile("<tr>.+?</tr>").matcher(html);
        int c = 1;
        while(m.find()){
            if(c++ == 3){
                System.out.println(m.group(0));
            }
        }
    }
}